Electric furnace



R. R. REED.

ELECTRIC FURNACE.

APPLICATION FILED MAR. 2?. 1920.

1,357,901 Patented Nov. 2, 1920.

FIG. 5. 1:1

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@Ho z n m I and tain new and useful Improvements in Elec- U'Ni'rsnSTATES ROBERT R. REED, 0F ITHACA, NEW YORK.

ELECTRIC FURNACE.

ASpefeicatioxi of` Letters Patent.

Patented Nov. 2, 1920.

LApplication led lI-arch 27, 1920. Serial No. 389,244.l

citizen of the United States of America, re-

sid at ithaca, in the county of rTompkins tate of New York, haveinvented 'cer-v tric Furnaces, of which the following is aspecification. u 4

The primary object ofthe invention is the provision of means forprotecting the'resstols of an electric furnace from oxidation,convection and deterioration, the method employed being one readilypractised and easily as well as inexpensively installed.

A further object of the invention is to increase the life of an electricfurnace substantially indefinitely bythe preservation of carbon on'otherresistors employed in the furnace,j, a protective 'envelop beingemployed failingto give up oxygen to the carbon and also cutting oil'convection.

A still `further object of .the invention is to provide a carbonresistance furnace preventingdisintegration of the resistors due tooxidizing and 'the effect of air currents 'traveling along the 'face ofthe resistor disintegratingparticles thereof, the .invention providingyielding heat-insulation for the resistors' as well as mounting thelatter yieldinglv'in the furnace.

Vith these general objects in view and others that will appear as thenature of the invention is better understood, the same consists ofthefmethod hereinafter set forth which will be described in connectionwith one manner of carrying out the saine as illustrated in theaccompanying drawing.

ln the drawing like reference characters designate corresponding partsthroughout 'the several views, and

'Figure 1 is a vertical transverse sectional view of theinvention,

F ig. 2 is a top plan view thereof with the top' plate `removed, and

Figs.A 3., et, and 5 are detail views of different forms of resistorsadaptable for employment with my furnace in carrying out theinventio'nfv My'mcthod and apparatus broadly consiste" in the protectionof resistors in electric furnaces by means of liquid glass and l haveherein-illustrated an electric furnace comprising an outer container 10constructed of such material as fire brick or concrete and being a heatinsulator for the mechanical protectionof the heating chamber therein. Alining 11 for the container 10 consists of magnesia (Mg.) or powderedbrick dust and magnesia, thereby forming a heat insulating liner for thecontainer. A crucible preferably formed of graphite of suitabledimensions' with an open mouth 13 is centrally mounted within theheating chamber 14 upon blocks or abutments 15 in such a manner as toallow for expansion and contraction. M olten glass 16l surrounds thecrucible 12 within the chamber 14 and the magnesia lin'- ing 11contacting the glass 18 forms a cushion orresilient heat insulatortherefor. The glass 16 is first inserted in the chamber 14 in 'powderedform, a plurality of resistors ,17 being mounted in the chamber 14 withtheir lower ends resting upon small pedestals 18 of socket formpermitting slight lateral movement to 'the resistors during the expansinand contraction of the glass 16.

The resistors 17 are preferably carbon, owing to the high resistance,which decreases as the' temperature rises, leading in' e1ectrodes 19being connected to the upper ends of the resistors 17 and projectingoutwardly of the furnace through the lining l1 and container'l() forconnection with theelectrical service wires 20 leading from thegenerator, not shown. 'Any desired number of resistors 17 may beemployed, it being understood that the powdered glass 16 is heated bythe electrical current fiowing through the resistors 17, melting theglass `16 which 'flows around the resistors 17 'and ciucible 12 shuttingoli' all air and oxygen. The glass 16 forms none of the chemicalcombination with the material of either tle resistors 17 or Crucible 12andthe-glass wi l not appreciably partivith its oxygen content at anytemperature less than 1800o C.

The glass 16 to be emploved in my method and apparatus has a high Si()2content` such as glass having over eighty per cent. of SiQ2 in itsmake-up with the i'en'iainder chemically substantially equally resistantin deoxygenation. Suchv glass as Pyrex (('orning Glass Company) or anyglass having a high silicon oxid content may be employed. The `crucible12 is of any standard make such as Dixon X' Cofs Crucible. i'i themechanical side. the low coefficient of expansion (.0000063) preventsdestructive pressure between the crucible 12 and the electrodes 17-19und the surrounding walls 11-'-10,

the heat insulation 11 being of a yielding na-v ture as well as theshiftable mounting of the resistors 17 and theY crucible 12 also-'guardagainst such pressures of expansion and contraction efforts.

A cap or plate 21 covers the chamber 1e being formed of such material asconcrete, soapstone or other refractory material with a heat insulatinglining 22 of such material. as magnesia. Dierent forms of resistors 1Tmay be employed such as perforated plate resistors shown in lig. 3 andcylindrical as shown in Fig. 5. The resistor in Fig. 5 comprises arefractory tube 23 containing molten glass 241` and a central resistor25, the same being used in special cases where the glass bath 16 for allresistors 17 in common, appears to be unsatisfactory. Whichever form ofresistors is employed, the same are preferably spaced lequal distancesyapart around the Crucible 12 within the molten .glass 16. ein opening26 is provided in the cap 21 for gaining access to the Crucible mouth 13therebeneath, the construction of container being substantially thatusually employed in electric furnaces. Suitable arrangement may be madefor withdrawing the electrodes 19 so thatthe glass 16 after the firstheat run forms a solid Aenvelop for cooling which contains the resistors1'4" which can be replaced in the same form and is serviceable as arepair element.

My invention including' the method of einployiiig liquid glass for theprotection of electric furnace resistors is not limited to theconstruction of apparatus herein illustrated and while an embodimentthereof has ,electric furnaces from disintegration consisting insurrounding the resistors with liquid glass.

5. The method of protecting electric fur? nace elements fromdisintegration consisting in surrounding such elements with pulverizedglass whereby al rise in temperature ofthe resistors`produces a moltenglass envelop therefor.

6. A. method for protecting the resistors of an electric furnaceconsisting in surrounding the resistors with powdered glass in theheating chamber of the furnace and raising the temperature of theresistors Learner above the melting point of the glass forming a moltenglass envelop surrounding the rel sisters.' V

7. A method for protecting the resistors of an electric furnaceconsisting in surrounding the resistors with powdered glass in theheating chamber of the furnace and raising the temperature of -theresistors above the melting point of the glass forming a molten glassenvelop surrounding the resisters, and yieldingly mounting the resispensating for the eripansion and contraction of the glass.

10. The method of protecting the. resistors of an electric furnaceconsisting inthe pro- 1vision of a resilient heat insulating lining lforthe heating chamber of the furnace and providing molten glasssurrounding the resistors in contact with said lining whereby expansionand contraction is equalizcd.

11. rllhe method of protecting the Crucible and resistors of electricfurnaces consisting in providing a resilient heat insulating lining forthe chamber of the furnace with the crucible and resistors positionedtherein and the provision of molten glass surrounding the crucible andresistors within and in contact with said lining.

12. The method4 of protecting resistors for electric furnaces consistingin the provision ofa resilient lining ofl magnesia for the heatingchamber of the furnace andlproviding molten glass contacting said liningsurrounding the resistors and Crucible.

13. The method of protecting resistors for electric furnaces consistingin the-provision of a resilient lining of magnesia for the heatingchamber of the furnace and provid ing molten lass contacting said liningsui'- rounding t e resistor and Crucible and yieldingly mounting tieCrucible and resistors Within the molten glass of the heat-- ingchamber.

i 14. An electric furnace comprising a' container, a resilient heatlinsulating lui'ing therefor providing aheating chamber within thefurnace, electrically connected resistors within the heating chamber andmolten glass within said chamber surrounding said resistors.

sev

10' eating for expansion and contraction.

16. An electric furnace comprising a container of refractory material, aresihentheat insulating lining therefor formed of brick dust andmagnesia, electrically connected resistors inwardly of the lining,powdered glass surrounding.. the resistors adapted for assuming a moltenmass upon raising the temperature of the resistors in the furnace. Intestimony whereof I afix my si nature.

ROBERT R. R ED.

